Systems and methods for making blade sheaths

ABSTRACT

A method of making a sheath for an airfoil may include the steps of forming an upper sleeve and a lower sleeve, and forming a central portion bonded to the upper sleeve and the lower sleeve. The central portion may be formed by depositing a material on the upper sleeve and the lower sleeve. A portion of the material may be removed from at least one of the central portion, the upper sleeve, or the lower sleeve. The sheath may include a first flank, a central portion bonded to the first flank, and a second flank bonded to the central portion. The central portion may have a substantially uniform microstructure resulting from additive manufacturing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, and thebenefit of U.S. Ser. No. 15/374,676 filed Dec. 9, 2016 and entitled“SYSTEMS AND METHODS FOR MAKING BLADE SHEATHS,” which is herebyincorporated by reference in its entirety for all purposes.

FIELD

The disclosure relates generally to sheaths for airfoils in gas turbineengines.

BACKGROUND

Fans are complex rotating systems that may encounter undesirableconditions during normal operation. Fans may be subject to debrisentering an engine inlet. The debris may contact the blades of the fanat the leading edge, causing damage. Blade sheaths may protect theleading edge of fan blades. The blade sheaths are often made usingcostly techniques and/or techniques that may leave microstructuralanomalies.

Blade sheaths are typically produced using subtractive methods such asmilling and machining techniques. These techniques typically have a highcost, low productivity rates, and long lead times. Many othersubtractive methods considered for blade sheaths are limited indimensional accuracy, surface finish, material integrity, andthroughput.

SUMMARY

A method of making a sheath for an airfoil is provided. The methodincludes the steps of forming an upper sleeve and a lower sleeve, andforming a central portion bonded to the upper sleeve and the lowersleeve. The central portion may be formed by depositing a material onthe upper sleeve and the lower sleeve. A portion of the material may beremoved from at least one of the central portion, the upper sleeve, orthe lower sleeve.

In various embodiments, the material may be deposited using wire arcadditive manufacturing. The upper sleeve may be fixed relative to thelower sleeve prior to forming the central portion. The upper sleeve andthe lower sleeve may also be formed from a sheet metal. The centralportion may be formed by applying a heat source to a wire comprisingtitanium. The lower sleeve and the upper sleeve may be made of titanium,aluminum, nickel, steel, and/or their alloys. The sheath may be bondedto the airfoil with an adhesive. An internal surface of the centralportion may be formed having a curved geometry, and the internal surfacemay joins the upper sleeve and the lower sleeve. A protective coatingmay be formed on the internal surface.

A sheath for an airfoil is also provided. The sheath may include a firstflank, a central portion bonded to the first flank, and a second flankbonded to the central portion. The central portion may be depositedusing additive manufacturing.

In various embodiments, the central portion has a substantially uniformmicrostructure as a result of additive manufacturing. The first flankand/or second flank may be formed from a sheet of a metal includingtitanium, aluminum, nickel, and/or steel. The central portion may beformed from a titanium alloy. An inner surface may be formed with acurved surface to join the first flank and the second flank. The innersurface may be substantially smooth with a substantially uniformmicrostructure.

A fan for a gas turbine engine is also provided. The fan may include ablade having a leading edge, a pressure side, a suction side, and atrailing edge. A sheath may be bonded to the blade by an adhesive. Thesheath may have a first flank on the pressure side, a second flank onthe suction side, and a central portion joining the first flank and thesecond flank. The central portion may have a substantially uniformmicrostructure.

In various embodiments, the central portion may be formed by applying aheat source to a wire to deposit material on the first flank and thesecond flank. The sheath may comprise at least one of titanium,aluminum, nickel, or steel. An inner surface of the central portion thatjoins the first flank and the second flank may be substantially smooth.

The forgoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated hereinotherwise. These features and elements as well as the operation of thedisclosed embodiments will become more apparent in light of thefollowing description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosures, however, maybest be obtained by referring to the detailed description and claimswhen considered in connection with the drawing figures, wherein likenumerals denote like elements.

FIG. 1 illustrates an example of a gas turbine engine, in accordancewith various embodiments;

FIG. 2A illustrates an elevation view of a blade having a sheath coupledto the blade, in accordance with various embodiments;

FIG. 2B illustrates a cross-sectional view of a blade with a sheath asviewed from top to bottom, in accordance with various embodiments;

FIG. 2C illustrates a front view of a sheath for a blade, in accordancewith various embodiments;

FIG. 3A illustrates a disconnected suction side flank and pressure sideflank of a sheath for a blade, in accordance with various embodiments;

FIG. 3B illustrates flanks of a sheath joined by a central portionformed by additive manufacturing, in accordance with variousembodiments;

FIG. 3C illustrates a finished sheath with a central portion depositedby additive manufacturing to join flanks of the sheath, in accordancewith various embodiments;

FIG. 4A illustrates a layered microstructure of a central portion of asheath deposited by additive manufacturing, in accordance with variousembodiments; and

FIG. 4B illustrates a granular microstructure of a sheath made usingadditive manufacturing, in accordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration and their best mode. While these exemplary embodiments aredescribed in sufficient detail to enable those skilled in the art topractice the disclosures, it should be understood that other embodimentsmay be realized and that logical, chemical, and mechanical changes maybe made without departing from the spirit and scope of the disclosures.Thus, the detailed description herein is presented for purposes ofillustration only and not of limitation. For example, the steps recitedin any of the method or process descriptions may be executed in anyorder and are not necessarily limited to the order presented.Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact.

Referring now to FIG. 1, an exemplary gas turbine engine 20 is shown, inaccordance with various embodiments. Gas turbine engine 20 may be atwo-spool turbofan that generally incorporates a fan section 22, acompressor section 24, a combustor section 26 and a turbine section 28.Alternative engines may include, for example, an augmentor section amongother systems or features. In operation, fan section 22 can drive fluid(e.g., air) along a bypass-flow path B while compressor section 24 candrive coolant along a core-flow path C for compression and communicationinto combustor section 26 then expansion through turbine section 28.Although depicted as a two-spool turbofan gas turbine engine 20 herein,it should be understood that the concepts described herein are notlimited to use with two-spool turbofans as the teachings may be appliedto other types of turbine engines including turbojet, turboprop,turboshaft, or power generation turbines, with or without geared fan,geared compressor or three-spool architectures.

Gas turbine engine 20 may generally comprise a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A-A′ relative to an engine static structure 36 viaseveral bearing systems 38, 38-1, and 38-2. It should be understood thatvarious bearing systems 38 at various locations may alternatively oradditionally be provided, including for example, bearing system 38,bearing system 38-1, and bearing system 38-2.

Low speed spool 30 may generally comprise an inner shaft 40 thatinterconnects a fan 42, a low-pressure compressor 44 and a low-pressureturbine 46. Inner shaft 40 may be connected to fan 42 through a gearedarchitecture 48 that can drive fan 42 at a lower speed than low speedspool 30. Fan 42 (or other rotating sections having airfoils such ascompressor section 24 or turbine section 28) may include a protectivesheath along the leading edge of the airfoils. Geared architecture 48may comprise a gear assembly enclosed within a gear housing that couplesinner shaft 40 to a rotating fan structure. High speed spool 32 maycomprise an outer shaft 50 that interconnects a high-pressure compressor52 and high-pressure turbine 54. Airfoils 55 coupled to a rotor ofhigh-pressure turbine may rotate about the engine central longitudinalaxis A-A′ or airfoils 55 coupled to a stator may be rotationally fixedabout engine central longitudinal axis A-A′.

A combustor 56 may be located between high-pressure compressor 52 andhigh-pressure turbine 54. Inner shaft 40 and outer shaft 50 may beconcentric and rotate via bearing systems 38 about the engine centrallongitudinal axis A-A′, which is collinear with their longitudinal axes.As used herein, a “high-pressure” compressor or turbine experiences ahigher pressure than a corresponding “low-pressure” compressor orturbine.

The core airflow along core-flow path C may be compressed bylow-pressure compressor 44 then high-pressure compressor 52, mixed andburned with fuel in combustor 56, then expanded over high-pressureturbine 54 and low-pressure turbine 46. Turbines 46, 54 rotationallydrive the respective low speed spool 30 and high speed spool 32 inresponse to the expansion.

With reference to FIGS. 2A, 2B, and 2C, blade 130 with sheath 132 isshown according to various embodiments. Blade 130 may be a blade of fan42 of FIG. 1, for example, and may also be referred to as an airfoil.Blade 130 with leading edge 136, trailing edge 138, tip 140, root 142,suction side 144 and pressure side 146, and sheath 132. Sheath 132includes solid portion 148 covering leading edge 136 with and taperedflanks 150 extending from each side of solid portion 148 to cover atleast a portion of suction side 144 and pressure side 146.

In various embodiments, sheath 132 covers leading edge 136 of blade 130with solid portion 148 by adhesively bonding the tapered flanks 150 tosuction side 144 and pressure side 146 of blade 130 with a scrim sheetbetween sheath 132 and blade 130. Tapered flanks 150 can be bonded tosuction side 144 and pressure side 146 with various adhesives including,but not limited to, rubber, synthetic rubber, silicone or epoxy resin. Ascrim sheet can be a thin textile which provides a separation betweenthe different materials of sheath 132 and blade 130, protecting blade130 from its susceptibility to galvanic corrosion where sheath 132 isbonded to blade 130.

Sheath 132 can be made of titanium, aluminum, nickel, or steel(including alloys of any) or other materials with sufficient stiffness,strength and erosion resistance to withstand the impact loads, staticand fatigue loads, or particulate and rain erosion that may beexperienced on the leading edge of an airfoil. The length of solidportion 148 (extending out from leading edge 136 and from tip 140) canvary widely, but may be sufficiently long to provide protection forleading edge 136 of blade 130. The length of tapered flanks 150 can bevaried on each side of blade 130 depending on various designconsiderations of blade 130 and sheath 132. In the example shown,tapered flank 150 on pressure side extends further in the chord-wisedirection to provide extra large scale impact protection such as a birdstrike, for example, in portions of blade 130 where blade 130 isvulnerable to impacts.

Sheath 132 provides extra strength and stiffness to blade 130, allowingblade 130 to be made of lightweight materials. Solid portion 148 ofsheath 132 provides a layer of protection from impact loads as well aserosion for leading edge 136 of airfoil. Tapered flanks 150 bond thesolid portion 148 to airfoil to hold the solid portion 148 in place.Additionally, leading edge 136 of solid portion 148 can be coated with athin layer of erosion resistant coating to provide increased erosionresistance. This coating may be a cermet, for example, WC or Cr₂C₂containing material, or a harder metallic material such as nick orcobalt based hard alloys. Other coating materials may also be suitablefor surfaces of sheath 132. Tapered flanks 150 may further providestiffness to blade 130 as well as surface area for a smooth loadtransfer during impacts to blade 130.

FIGS. 3A, 3B, and 3C illustrate the process of making a sheath 170 usingadditive manufacturing, in accordance with various embodiments. In FIG.3A, upper sleeve 172 and lower sleeve 174 are formed separately.Although the terms upper sleeve and lower sleeve are used with referenceto the cross-sectional view of FIG. 3A to distinguish the two sleeves,no specific orientation is meant to be implied by the labels upper andlower. Upper sleeve 172 and lower sleeve 174 may be formed in a shapesimilar to tapered flanks 150 described above. Upper sleeve 172 andlower sleeve 174 may be formed from a metallic material. Upper sleeveand lower sleeve may be formed from titanium, aluminum, nickel, steel,alloys thereof, or other metallic materials. Upper sleeve 172 and lowersleeve 174 may be formed of the same material, or of different materialsin various embodiments. For example, upper sleeve 172 and lower sleeve174 may be formed from sheet metal comprising titanium alloy. Uppersleeve 172 and lower sleeve 174 may be long sheets of material that havea contour matching a blade 130 (of FIG. 2A) along the pressure side orsuction side.

Upper sleeve 172 and lower sleeve 174 may be formed using varioustechniques including hot forming, rolling, machining, sheet metal,extrusion, and/or additive manufacturing. Upper sleeve 172 and lowersleeve 174 may be formed as completely disconnected sleeves and laterconnected. Upper sleeve 172 and lower sleeve 174 may also be formed aspartially connected or connected sleeves suitable for deposition of acentral leading edge.

In FIG. 3B, additive manufacturing technology is used to join the uppersleeve 172 and lower sleeve 174 by building a central portion 176. Uppersleeve 172 and lower sleeve 174 may be clamped to a mandrel or othermechanical device, for example, to hold or fix the sleeves in positionrelative to one another. In various embodiments, wire arc additivemanufacturing (WAAM) may be used to build central portion 176. To useWAAM, an electric arc such as a tungsten inert gas (TIG) or metal inertgas (MIG) source, for example, may be used as heat source 182. A wire184 as may be used as feedstock. WAAM may further include using weldingpower sources, torches, and/or wire feeding systems to deposit materialfrom wire 184 onto a workpiece such as central portion 176, for example.Upper sleeve 172 and/or lower sleeve 174 may be micro-roughened prior todeposition of central portion 176 to improve bonding characteristics.

The WAAM process may use arc control systems to robotically depositmaterial. In response to wire threading, wire 184 may be fed in thedirection of the central portion 176 and make contact. The controlsystem may detect wire 184 in contact with central portion 176 andretract the wire until it wire 184 at a desired ignition distance fromthe central portion 176. Motion may be provided by robotic systems toposition wire 184 at the desired location relative to central portion176 and apply the heat source to the wire. Central portion 176 mayinclude a bond line 178 where central portion 176 is deposited on andbonded to upper sleeve 172 and lower sleeve 174. Central portion 176 mayalso include rough surfaces 180 in an unfinished form.

In FIG. 3C, a post build thermo-mechanical treatment and/or finalmachining is performed on sheath 170. Sheath 170 may be shaped into itsfinal dimensions using machining to remove material, though othertechniques may also be used. A thickness T₁ of upper sleeve 172 at adistal end may be approximately 0.040 inches (1.02 mm). The termapproximately as used with dimensions is meant to mean a variety ofpossible ranges including +/−5%, +/−10%, +/−15%, or +/−20, for example.Lower sleeve 174 may be generally thinner than upper sleeve 172. Lowersleeve 174 may have a thickness T₂ at a distal end of approximately0.020 inches (0.51 mm). The thickness of lower sleeve 174 and uppersleeve 172 may increase with proximity to central portion 176. Lowersleeve 174 and upper sleeve 172 may form the tapered flanks 150 (of FIG.2A). Central portion 176 may have a thickness T₃ of approximately 1-2inches. Internal surface 188 of joining the upper sleeve 172 and lowersleeve 174 may be a curved surface. The curve may be radial ormulti-radial, hyperbolic, or any other suitable curve. For example,internal surface 188 may have a radius of curvature of approximately0.040 inches (1.02 mm). Outer surface 190 and internal surface 188 maybe finished into smooth surfaces and treated with optional protectivecoatings to reduce corrosion and/or improve ware characteristics. Innerportion 192 of central portion 176 may be formed deposited material witha uniform microstructure.

With reference to FIGS. 4A and 4B, a microstructure of a sheath 132 (ofFIG. 2A) formed using additive manufacturing is shown, in accordancewith various embodiments. Sheaths formed using the additivemanufacturing as described herein may also improve quality byeliminating microstructure flaws generated by traditional techniques,such as forming internal folds and crack at internal surface 188 (ofFIG. 3C). Microstructure 200 of FIG. 4A illustrates various layers 202with bond lines 204 where each layer of material was deposited usingadditive manufacturing. Microstructure 200 illustrates a multi-layertitanium alloy wall built using WAAM. FIG. 4B illustrates asubstantially uniform microstructure 210 of a titanium deposit 212. Themicrostructures of FIGS. 4A and 4B are substantially uniform and mayhave improved strength characteristics compared to less uniformmicrostructures. A substantially uniform microstructure may also lackfolds and cracks associated with various manufacturing technologies.

Components made using WAAM may include a grain structure grown in thedirection of material being added. The surfaces of a sheath made withadditive manufacturing may thus be smooth. The sheaths may have internalstructural details that cannot be machined into the components due tolack of access such as, for example, internal surface 188 of FIG. 3C.

Surfaces made using WAAM, EBAM, or similar weld-like techniques maydeposit material in a series of cylindrical layers formed one on top ofanother. A wall formed by the techniques may thus have varying widthcorresponding to the cylindrical profile of each layer. The strength ofthe wall, however, may be limited by the thin portions of the wall.Thus, the excess material may be removed from each layer during thedeposition process or after the deposition process. In that regard,forming a sheath of the present disclosure using WAAM and/or EBAMmanufacturing may also include depositing a layer of material, removingexcess material from the layer to give the layer a substantially smoothsurface, depositing another layer of the layer of uniform width, andremoving the excess material from the second layer to give the secondlayer a substantially smooth surface. This process may be continuedthroughout the build of the entire sheath. In various embodiments of thebuild process, several layers of material could be deposited, followedby a clean-up process which would remove excess material from the entirewall surface, creating a wall with a substantially smooth surface.

In various embodiments, sheaths of the present disclosure formed usingadditive manufacturing may be formed with greater productivity rates.For example, the WAAM build rate may be 3 time higher than laser powderdeposition. The additive manufacturing techniques described herein mayreduce the cost associated with sheath production by eliminating costlyhot forming operations and greatly reducing machining of externalsurfaces.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosures.

The scope of the disclosures is accordingly to be limited by nothingother than the appended claims, in which reference to an element in thesingular is not intended to mean “one and only one” unless explicitly sostated, but rather “one or more.” Moreover, where a phrase similar to“at least one of A, B, or C” is used in the claims, it is intended thatthe phrase be interpreted to mean that A alone may be present in anembodiment, B alone may be present in an embodiment, C alone may bepresent in an embodiment, or that any combination of the elements A, Band C may be present in a single embodiment; for example, A and B, A andC, B and C, or A and B and C. Different cross-hatching is usedthroughout the figures to denote different parts but not necessarily todenote the same or different materials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”, “anexample embodiment”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiment.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element is intended to invoke 35 U.S.C. 112(f)unless the element is expressly recited using the phrase “means for.” Asused herein, the terms “comprises”, “comprising”, or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus.

What is claimed is:
 1. A sheath for an airfoil comprising: a first flankhaving a contour matching a suction side of the airfoil; a centralportion bonded to the first flank, wherein the central portion isdeposited using additive manufacturing; and a second flank bonded to thecentral portion and having a contour matching a pressure side of theairfoil.
 2. The sheath of claim 1, wherein the central portion comprisesa substantially uniform microstructure.
 3. The sheath of claim 2,wherein the first flank is formed from a sheet of a metal.
 4. The sheathof claim 3, wherein the metal comprises at least one of titanium,aluminum, nickel, or steel.
 5. The sheath of claim 1, wherein thecentral portion comprises a titanium alloy.
 6. The sheath of claim 1,further comprising an inner surface having a curved surface to join thefirst flank and the second flank.
 7. The sheath of claim 6, wherein theinner surface is substantially smooth with a substantially uniformmicrostructure.
 8. A fan comprising: a blade having a leading edge, apressure side, a suction side, and a trailing edge; and a sheath bondedto the blade by an adhesive, wherein the sheath comprises a first flankon the pressure side, a second flank on the suction side, and a centralportion joining the first flank and the second flank, wherein thecentral portion comprises a substantially uniform microstructure.
 9. Thefan of claim 8, wherein the central portion is formed by applying a heatsource to a wire to deposit material on the first flank and the secondflank.
 10. The fan of claim 8, wherein the sheath comprises at least oneof titanium, aluminum, nickel, or steel.
 11. The fan of claim 8, whereinan inner surface of the central portion that joins the first flank andthe second flank is substantially smooth.